What I Learned From AFNetworking's GitHub Issues

(Presented at NYC iOS Developer Meetup & CocoaConf Columbus 2012)

It can be said that GitHub Issues are the hacker's equivalent of the classical Greek forum. Like the ancient philosophers before us, here the leading minds in open source gather to discuss the programming topics of our day. In this talk, we'll dig through AFNetworking's backlog to discover and dissect the epic debates, lofty ideas, and occasionally-fierce rhetorical exchanges contained within those hallowed threads.

Transcript

1. What I Learned From AFNetworking's GitHub Issues Mattt Thompson Mobile Lead, Heroku
5. Lessons Learned
6. Lesson 1: Designing Great Software Means Saying No... A Lot
7. Every Line of Code Needs to Justify its Own Existence
8. Every Feature Adds Complexity
9. • Ordered Query String Parameters • Customizable Query String Format • Property for DELETE Parameters to be in either Query String or Message Body • Retry Parameter for Operations • Option to Parse Top-Level JSON Fragments
10. ARC w/Macros
12. Lesson 2: If You Can’t Give Them What They Want, Give Them Something Better
14. Feature Requests are Data Points to Understand What Should Be Improved
15. Custom Mime Types
17. • application/json • application/javascript
18. • application/json • application/javascript • text/javascript
19. • application/json • application/javascript • text/javascript • text/x-javascript • text/x-json • application/x-javascript
21. application/vnd.github+json
22. AFHTTPRequestOperation +addAcceptableContentTypes:
23. JSON Libraries
24. • JSONKit • yajl_json • SBJSON • TouchJSON • NextiveJSON
26. AFJSONUtilities.h AFJSONEncode() / AFJSONDecode()
27. NSData * AFJSONEncode(id object, NSError **error) { NSData *data = nil; SEL _JSONKitSelector = NSSelectorFromString(@"JSONDataWithOptions:error:"); SEL _YAJLSelector = NSSelectorFromString(@"yajl_JSONString"); id _SBJsonWriterClass = NSClassFromString(@"SBJsonWriter"); SEL _SBJsonWriterSelector = NSSelectorFromString(@"dataWithObject:"); id _NXJsonSerializerClass = NSClassFromString(@"NXJsonSerializer"); SEL _NXJsonSerializerSelector = NSSelectorFromString(@"serialize:"); id _NSJSONSerializationClass = NSClassFromString(@"NSJSONSerialization"); SEL _NSJSONSerializationSelector = NSSelectorFromString(@"dataWithJSONObject:options:error:"); #ifdef _AFNETWORKING_PREFER_NSJSONSERIALIZATION_ if (_NSJSONSerializationClass && [_NSJSONSerializationClass respondsToSelector:_NSJSONSerializationSelector]) { goto _af_nsjson_encode; } #endif if (_JSONKitSelector && [object respondsToSelector:_JSONKitSelector]) { NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:[object methodSignatureForSelector:_JSONKitSelector]]; invocation.target = object; invocation.selector = _JSONKitSelector; NSUInteger serializeOptionFlags = 0; [invocation setArgument:&serializeOptionFlags atIndex:2]; // arguments 0 and 1 are self and _cmd respectively, automatically set by NSInvocation if (error != NULL) { [invocation setArgument:error atIndex:3]; } [invocation invoke]; [invocation getReturnValue:&data]; } else if (_SBJsonWriterClass && [_SBJsonWriterClass instancesRespondToSelector:_SBJsonWriterSelector]) { id writer = [[_SBJsonWriterClass alloc] init]; NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:[writer methodSignatureForSelector:_SBJsonWriterSelector]]; invocation.target = writer; invocation.selector = _SBJsonWriterSelector; [invocation setArgument:&object atIndex:2]; // arguments 0 and 1 are self and _cmd respectively, automatically set by NSInvocation [invocation invoke]; [invocation getReturnValue:&data]; [writer release];
28. NSJSONSerialization
29. ASINetworkQueue
30. ASIHTTPRequest
31. ASINetworkQueue
32. AFHTTPClient -enqueueBatchOfHTTPRequestOperations: progressBlock: completionBlock:
33. Lesson 3: Never Merge In Code That You Don’t Understand
34. Lesson 3: Never Merge In Code That You Don’t Understand
35. dispatch_group
36. AFHTTPClient -enqueueBatchOfHTTPRequestOperations: progressBlock: completionBlock:
37. 1 2 3 4 5 Batch
38. 1 2 3 4 5 Batch
39. 1 2 3 4 5 Batch 1 2 3 4 5 1 2 3 4 5
40. Thread Safety
43. Lesson 4: Don’t Settle For Not Understanding Something
44. Thread Safety
45. MVC Networking
51. • dispatch_async pattern • Dedicated Network Thread • Custom Dispatch Queues for Background Processing
52. “The Deallocation Problem”
54. When you start a secondary thread, it's common for that thread to retain the target object. If you don’t ensure that the thread releases that reference before the main thread releases its last reference to the object, bad things happen.
55. - (void)setCompletionBlock:(void (^)(void))block { if (!block) { [super setCompletionBlock:nil]; } __block id _blockSelf = self; [super setCompletionBlock:^ { block(); [_blockSelf setCompletionBlock:nil]; }]; }
56. API Consistency
58. AFHTTPClient -HTTPRequestOperationWithRequest: success: failure: AFHTTPRequestOperation -setCompletionBlockWithSuccess: failure:
59. Lesson 5: The More You Put In, The More You Get Out
60. •Be Present •Be Nice •Be Socratic 3 Rules for Project Ownership
62. Thanks!